The present invention relates to a delivery-valve unit on a compensating tank in the cooling circuit of an internal-combustion engine and, more particularly, to a valve unit which is inserted in a receiving housing arranged within the tank cover and consists of a first relief valve and a second relief valve, following the first relief valve. The valves each consist of a valve body closing a valve orifice by a spring and a float controlling an overflow bore located between the two relief valves.
A conventional delivery-valve unit is shown in EPA 0,180,208. The disadvantage of this arrangement of a delivery-valve unit on a compensating tank is, however, that the valve unit bulges together with the tank in the event of a pressure rise in the tank such that the valve sealing surfaces subjected to pressure on one side become distorted and leaks occur.
An object of the present invention is to provide a delivery-valve unit in which leaks brought about by dimensional changes in the compensating tank are avoided.
In accordance with the present invention, the foregoing object has been achieved by arranging the relief valves in valve housings which are separate from the compensating tank and which are inserted sealingly in a receiving housing. Two valve orifices are connected to the tank interior via respective overflow bores separated from one another. A float for controlling the overflow bore located between the relief valves is guided in the tank interior.
Thus, the provision of special valve housings affords new sealing surfaces for the relief valves in those valve housings, thereby doing away with the previous sealing surfaces of the valves relative to the compensating tank. Because the sealing surfaces of the valve unit are uncoupled from the walls of the compensating tank, the sealing surfaces remain undisturbed by pressure stress in the event of a dimensional change in the compensating tank.
A further advantage of the present invention is provided by the feature in which the valve-receiving housing is horizontally arranged, enclosing the two valve housings together with the valves, on the cover of the compensating tank, since, contrary to known configurations, space is saved in the upper part of the engine compartment.
An additional advantageous arrangement of a delivery-valve unit of the present arrangement resides in a rib extending longitudinally or transversely in the tank cover and forming the termination of an intermediate wall inside the tank with the cover ensures greater stability of the valve unit and greater protection of the valve elements. Under pressure stresses in the tank, the intermediate wall acts in the manner of a tie rod for the cover.
Another advantageous feature of the valve unit according to the present invention is a connection of the two valve housings by way of a snap engagement which makes handling easier during the coupling of valve housings.
Finally, the use of O-ring gaskets in the arrangement of the present invention guarantees adherence to distortion tolerances as regards leakproofing and constitutes a costeffective sealing alternative.